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When should a non-aggressive exotic species be demoted to a harmless naturalized resident?

By Dr. Laurel Haavik, US Forest Service

Exotic species that establish, spread, and cause substantial damage are demonized as foreign invaders that charge with menacing force across the landscape. Rightly so; those pests threaten to displace or eliminate native species and alter ecosystem functions. Chestnut blight, emerald ash borer, and hemlock woolly adelgid are all excellent examples. What about invaders that aren’t so destructive? Or, at least don’t seem to be at the moment? At what point do we stop monitoring a seemingly innocuous invasive species, especially one that has proved itself a serious pest elsewhere? To make this decision, it’s helpful to know how much the species has affected its new habitat, and whether this impact already has or is likely to change over time. That is exactly what we set out to do with the European woodwasp, Sirex noctilio, in Ontario.

Nearly a decade after the woodwasp was first found in a trap near the Finger Lakes in New York (and then a year later across Lake Ontario in Sandbanks Provincial Park), it still hadn’t killed pines in noticeable numbers, either in the US or Canada. Native to Europe and Asia, this woodwasp has been introduced to several countries in the Southern Hemisphere, where it has been a serious pest in forests planted with exotic pines. By contrast, in North America, it seems that only the weakest trees, those that are already stressed by something else, are killed by the woodwasp. Would forests with many weakened trees allow populations of the woodwasp to build up enough that they could then kill healthy trees in well-maintained forests? Could we find any evidence that this had already happened or would likely happen in the future?

Our goal was to measure the impact the woodwasp has had in Ontario, and whether that has changed over time, by closely examining the same trees in pine forests every year. First, we had to find sites where the woodwasp could be found, which wasn’t every pine forest, and where landowners would allow us to work. We were not interested in sites that were well-managed, because research had already confirmed that the woodwasp was not present in those forests. We used records of positive woodwasp captures from the Ontario Ministry of Natural Resources trap survey as a guide. We visited 50 potential sites, and eventually selected eight for close scrutiny in our long-term study. These sites were areas where there was likely to be intense competition among trees for resources, with plenty of stressed trees for the woodwasp.

The European woodwasp was probably absent from a well-managed red pine forest (left), but likely to be found in an un-managed scots pine forest (right).

We visited all eight sites every fall from 2012 to 2016, after woodwasps had the opportunity to attack trees. Adult woodwasps mate and lay eggs, attacking trees in the process, in mid-summer. Attack was visible as distinctive resin beads scattered over the trunk. We recorded which trees had been attacked, and later (usually the following year) killed by the woodwasp.

The woodwasp population was considerable at some of our sites, having killed about one-third of the trees within five years. Though at other sites, the population was much smaller, having killed only a small percentage of trees. We’re not exactly sure what caused this variability. It’s possible that the woodwasp arrived at some of our sites years before it arrived at others, and the most vulnerable trees were long dead at the sites it invaded earlier. We have no record of time since woodwasp invasion at any of our sites. It’s also possible that local environmental conditions, which we did not measure, could in some way have affected tree resistance or the woodwasp population.

Most curious, though, was that over the five years many trees attacked by the woodwasp did not die – around 50 to 80%. At least half of these trees were attacked again and again in successive years. We had captured an interesting part of the woodwasp’s ecology, its way of essentially priming trees to become better habitat for its young. When laying eggs, female woodwasps also inject a self-made toxic venom along with a symbiotic fungus into the tree, to help kill it. If the tree is sufficiently resistant to attack, the female may not lay eggs, only the fungus and venom. The fungus and venom then work in concert to weaken (prime) the tree for re-attack – and hopefully successful colonization – in subsequent years.

Female woodwasps sometimes die while laying eggs. Survival of the fittest?

Two-thirds of trees that were attacked by the woodwasp at some point in our study (one or more times) did not die, which shows that most trees selected by the woodwasp as suitable habitat are at the moment resistant to its advances. This also shows, along with the variability in woodwasp impact among sites, that this invader is active in the forest. Should environmental conditions change (say, if a drought occurs), woodwasp populations could quickly rise to outbreak levels, which could kill large numbers of healthy pines. This has happened in other places.

Long-term study of these sites, and hopefully others, is needed so that we can be aware of changes that arise in woodwasp impact. This will allow us to be proactive about what steps to take to manage this invader, should it become a problem. It will also help us better understand and predict what causes exotic species to vacillate on the spectrum between aggressive invader and innocuous resident.

Want to read more? Check out the original article published in The Canadian Entomologist, which is freely available for reading & download until May 14, 2018.

Haavik, L.J., Dodds, K.J. & Allison, J.D. (2018) Sirex noctilio (Hymenoptera: Siricidae) in Ontario (Canada) pine forests: observations over five years. The Canadian Entomologist, 1–14. doi: 10.4039/tce.2018.18

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When Adventure Comes Calling ~ Foreign Perspectives

By Paul Manning, Post-doctoral Researcher, Dalhousie University

Sometimes when you’re least expecting it you can find yourself presented with the adventure of a lifetime. This recently was the case for me. My adventure took me to the United Kingdom, from September 2013 to August 2016, where I completed my DPhil in Zoology at the University of Oxford.

I didn’t have any long-standing plan to attend the University of Oxford. While finishing my undergraduate degree at the Faculty of Agriculture at Dalhousie University (Truro, Nova Scotia), I decided to apply for a Rhodes scholarship on a bit of a whim. The application was daunting but nonetheless, I managed to put something together and received word that I was a regional finalist. Roughly a week before my final interview, I scanned the University of Oxford – Department of Zoology website and came across the name Owen Lewis. I read through a couple of his papers and sent him a quick e-mail explaining my situation. I received a near-immediate response. Owen enthusiastically wished me the best of luck with my interview and agreed to act as my supervisor should I receive funding. Through a combination of luck, privilege and merit I found myself presented with the opportunity to study at the University of Oxford. I submitted my application to the university a week later. Opting to spend three years being supervised by a stranger based on a single e-mail exchange is not something I would advise to others, but it is exactly what I chose to do. Fortunately, I landed in an incredibly supportive and inclusive research group – and Owen’s first exchange perfectly predicted his supervisory style: helpful, available, and incredibly kind.  

I fell in immediate love with the city of Oxford soon after my arrival. The first thing you might notice about the city is the architecture: medieval walls, ivory towers, and ancient gates seem to appear around every corner. The second thing you might notice is all the bikes – they easily outnumber the cars on the road. The squealing of rusty brakes and pinging of bells is the soundtrack of a morning commute. The third thing you might notice is the gigantic slugs and snails that appear at night – that was my experience at least.

Looking West down High Street Oxford from the top of the Magdalen Tower (L). A delightful garden snail (Limax flavus) that would greet me at the entrance to my flat (M). A delightfully plump slug (Cornu aspersum) with a pound coin for scale (R).

My DPhil research explored the importance of insect biodiversity in perturbed environments using dung beetles as a model system. I did a fair amount of my fieldwork in Southwest Wales, where I was introduced to my co-supervisor Sarah Beynon. Sarah had recently completed her DPhil with Owen as a supervisor and was in the process of setting up “Dr Beynon’s Bug Farm”, which is probably best described as a mixture between a research centre, tropical insect zoo, and working farm. It also is home to Grub Kitchen, UK’s first restaurant with edible insects on the menu.  I spent my first summer living and researching on-site, while the start-up was in its initial stages. It’s a beautiful place – in the early spring the farm is blanketed with yellow iris, red campion, and various orchid species. It was a short bike ride to the coast which I frequented to enjoy steep paths, white sands, and impressive waves.

One of the things that I truly loved about the United Kingdom was the widespread appreciation and knowledge of natural history. The entomology and ecology circles that I ran in certainly would have amplified this signal, but it seemed to run deep in society-at-large. When a server interrupts your book-in-face breakfast to offer her insights about myxomatosis, a viral disease of rabbits, you might just be in the United Kingdom.

A late afternoon rainbow spotted at the Bug Farm (L). Some red campion (Silene dioica) blooming near St. David’s, Pembrokeshire UK (M). Blue skies and strong current on the Ramsey Sound (R).

Some of my favourite memories from my time abroad were natural history outings. Richard Comont, a DPhil student in our research group took me out in the winter of 2014 to see the impressive minotaur dung beetle. We arrived at a local park in the pitch black of night, armed with a couple flashlights. Richard, who bears a certain resemblance to Hagrid (the brawny groundskeeper for Hogwarts School of Witchcraft & Wizardry), also carried a pooter, umbrella, and beating stick. We found the minotaur beetles, they were certainly impressive, but perhaps more memorable was a vivid image of a grinning Richard whaling on a bit of gorse with a broom stick, in the pitch black of the woods.

Another dung beetle memory involves Darren Mann, Head of the Life Collections at the Oxford University Museum of Natural History. Darren invited me out for a day of dung beetle recording as part of a Scarabaeoidea recording effort known charmingly as Team DUMP. We left at six in the morning, drove two-and-a-half hours to rural Wales, and sifted through animal dung on sand dunes until it was so dark that we couldn’t see our hands in front of us. Darren found one species he expected was locally extinct – upon realizing what he found, he gave a fantastic howl of excitement. I’d expect there are few people who are more enthusiastic and knowledgeable about insects than is Darren Mann. If you ever get the chance, make sure to ask him about cockroaches sometime.

A third dung beetle memory is a day I spent collecting with Sarah and her partner Andy. We were getting ready to run a few experiments, and set-up a dung beetle demonstration at a tradeshow. Of course, the powers that be sent along torrential rain. To this day, I don’t think there is a more miserable feeling than kneeling in prickly shrubs, soaked to the bone, sifting through sheep dung. Nonetheless, that’s what we did for hours and hours. Upon returning to the vehicle, I cleaned up and towelled off only to have a bird defecate directly onto my head and shoulder. There couldn’t have been a more fitting end to the day.

An impressive Minotaur beetle (Typhaeus typhoeus) in Shotover Country Park, Oxfordshire (L). A vial of dung beetles containing 104 Onthophagus joannae removed from a single pile of dog dung (Photo by Darren Mann) (M). A collection of beautiful Geotrupid beetles found on Ramsey Island (St. David’s, Pembrokeshire) (R).

While my experience in Oxford was overwhelmingly positive, it did not come without its challenges. The biggest challenge I encountered was dealing with low points caused by an all-encompassing imposter syndrome. The ease and speed at which my colleagues could process and synthesize information was nothing short of intimidating.  Meanwhile, I had trouble getting my first few experiments off the ground; while simultaneously everyone around me seemed to be successfully completing ground-breaking research. I felt slow, unaccomplished, and lazy.  I tried to compensate by putting in additional time: arriving earlier, staying later, and working on weekends – but this just left me feeling burnt-out. Plenty of exercise, structuring my work days, limiting social media, and hours of conversation with my partner, friends, family, colleagues, and supervisors helped me get back on my feet.

I’ve been home in Canada since the summer of 2016, working as a post-doc and a sessional lecturer. I think often and fondly about my time spent abroad in the United Kingdom and would highly recommend it as a study destination. While competitive, there are many different funding sources that Canadian students can access, including the Commonwealth Scholarships, NSERC – Michael Smith Foreign Supplement, Rhodes Scholarships, as well as numerous other international scholarships offered at the institutional level. Living in a foreign country provides you with a fresh outlook and opens your world to a range of new experiences, ideas, and perspectives. If international study is compatible with your other commitments, mull it over a little, and think about giving it a shot – becoming an international student might be just the adventure you’ve been looking for.

Are you a Canadian resident spending time abroad to conduct entomological research, or are you coming to Canada for the opportunity to study? If you’d like to share your story and experiences as part of the Foreign Perspectives series, please get in touch with us by email.

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Behavioural observations in nature reveal mating strategies of jumping spiders

—- By Gwylim S. Blackburn & Wayne P. Maddison—-

Animals reveal a lot about their lives simply by the way that they behave. When observed in the wild, they also offer insights to the function of behaviours in a natural context. Capturing these insights just requires a little patience, and attention to the right details.

In a recent study printed in the journal Behaviour, we set out to document Habronattus americanus jumping spider behaviors that would shed light on their ‘mating strategies’—the tactics used by females and males to acquire mates. Specifically, we wanted to know if males show off their flashy displays only to females or also compete directly with each other, if they invest heavily in mate search, and if females are choosy when deciding who to mate with.

HamericanusMaleFront_Blackburn&Maddison

An adult male Habronattus americanus jumping spider travels through beach habitat in British Columbia, Canada. The bright coloration on his face and legs is presented to females during elaborate courtship dances. Photo credit: Sean McCann.

To pursue these issues, we followed 41 adults for up to 30 minutes each, and we also staged interactions between an additional 36 male-female pairs, in natural habitat.

Typical Habronattus americanus habitat is fairly flat, well-drained, and sparsely covered with plants, sticks, or pebbles. Photo credit: Maxence Salomon

Typical Habronattus americanus habitat is fairly flat, well-drained, and sparsely covered with plants, sticks, or pebbles. Photo credit: Maxence Salomon

The behaviours of both sexes pointed quite strongly to indirect male competition for choosy females. Males did not display to (or fight with) each other. Instead, they travelled far and wide, eating nothing but displaying to every female they met. Females, on the other hand, focused on hunting rather than travel, and they almost never permitted copulation despite the vigorous courtship efforts of males.

Collectively, these behaviours supply deeper lessons than their individual functions; they also indicate how natural selection might shape several of the traits involved. In particular, our findings suggest that female mate choice may be the key source of selection favouring the evolution of male display traits.

An adult female Habronattus americanus jumping spider in natural beach habitat. Females are avid hunters. Photo credit: Sean McCann

An adult female Habronattus americanus jumping spider in natural beach habitat. Females are avid hunters. Photo credit: Sean McCann

The apparently high investment by males in mate search also represents a potential factor shaping female mate preferences. In a variety of other species, mate search costs have been shown to provide a way for females to judge the quality of prospective mates. This is because males who are able to pay those costs while still producing an impressive display can make better fathers (e.g., by providing better parental care, or by passing along advantageous genes to their offspring). To determine if this is the case in H. americanus, further research will be needed to see how male condition is linked to the quality of their displays and the success of their offspring.

The Habronattus jumping spiders are famous for their stunning array of male displays. It would be fascinating to know how mating strategies, and the natural surroundings in which they unfold, have influenced this diversity. Behavioural observations of different species in the wild will be essential for getting at this question.

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From filing cabinets to fieldwork: an investigation into Aphid population variability

By Chris Buddle, Editor of the Canadian Entomologist

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I am pleased to present the “Editor’s Pick” manuscript for the current issue of The Canadian Entomologist. This pick was a paper by Bob Lamb, Patricia MacKay and Andrei Alyokhin, titled “Seasonal dynamics of three coexisting aphid species: implications for estimating population variability

I had always admired the ongoing work on aphids, spearheaded by Bob and Pat. Their work is always relevant, meticulous, framed in an important and broader ecological context, and they have a ‘model system’ to work with. This is the kind of researcher many more junior entomologists look up to.  The current paper is no exception. In this work, Bob and Pat joined up with Andrei Alyokhin and present a careful study of population variability and effectively use this metric to better understand population dynamics over time.  For me, I see much value in this approach, and can see how this kind of work could effectively be used in teaching students about how to best describe, understand, and quantify population dynamics.  I’m also inspired to see long-term data with arthropods. These kinds of data are so useful, but relatively rare. It’s great to see Bob, Pat and Andrei publish thoughtful and important work using such data.  I may also look around some old filing cabinets at my University…

Bob was kind enough to answer a few questions about this work, with input from his co-authors.

What inspired this work?

When Pat MacKay and I were anticipating eventual retirement from paying jobs as entomologists, we decided to begin a study of an aphid population that could be pursued as long as we could walk trails and count aphids. Our goal was to figure out why aphid populations seem to be so unstable. Eventually we wrote up our findings on the stability of one native species over the first 10 years of a study we hope will go on for at least another 10 years. A few years ago we realized we needed comparative data, but were too old to start on a 20-year study of another aphid species. The solution was to write to colleagues who also had long-term data sets, to see if they were interested in looking at their data from this perspective. So far the colleagues we have contacted have been enthusiastic collaborators. The first was Andrei Alyokhin our coauthor on the current paper. He gave us access to 60 years of data on three aphid species. The first paper on the stability of these aphids was published in the Canadian Entomologist two years ago. The current paper extends that earlier work, looking now at how aphid seasonal biology affects our estimates of stability.

Bob Lamb, sporting "aphid hunting gear"

Bob Lamb, sporting “aphid hunting gear”

What do you hope will be the lasting impact of this paper?

We hope that this paper will help convince other researchers that Joel Heath’s metric, PV, which we use to quantify population variability, is a robust way to quantify one aspect of the stability of populations. If more researchers adopt this metric, ecologists will have a much greater opportunity to apply a comparative approach and identify factors that contribute to stability or instability of populations.

Where will your next line of research on this topic take you?

Pat MacKay and I continue to extend our time series on the abundance of a native aphid, and are now focusing more on the ecological processes that cause our five populations to rise and fall. We also hope to expand our studies of stability to still more aphid species, but also species with very different life histories. At the moment I am working with a colleague, Terry Galloway, University of Manitoba, on several time-series of ectoparasite abundance on birds.

Do you have any interesting anecdotes about this research?

One of the most interesting aspects of the work on aphids from potatoes is the source of the data – 60 years or more of weekly aphid counts. The data for the early years were discovered by Andrei Alyokhin in an abandoned filing cabinet stored in a barn at the University of Maine. Andrei was a new faculty member at the time exploring his research facilities. His predecessors had maintained meticulous records of aphid densities in potato plots since soon after World War II. Andrei was quick to recognize the value of this data, and more importantly recognized the need to go on collecting the data in the same way. The result is an amazing data set, one of the longest continuous records at one location of the dynamics of multi-voltine species.

Lesson 1: newly-hired entomologists should begin their careers by searching old filing cabinets.

Lesson 2: meticulous long-term records can be invaluable, sometime in ways that you might not anticipate.

Andrei discovering data in old filing cabinets

Andrei discovering data in old filing cabinets

Lamb R.J., MacKay P.A. & Alyokhin A. (2013). Seasonal dynamics of three coexisting aphid species: implications for estimating population variability, The Canadian Entomologist, 145 (03) 283-291. DOI:

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Canadian Entomologist Editor’s Pick – March 2013

By Chris Buddle, editor of The Canadian Entomologist

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The Canadian Entomologists’ latest issue is devoted to Arctic Entomology, with guest editors Derek Sikes and Toke T. Høye putting together an excellent suite of papers on this topic.  This is a very timely issue – there is an incredible amount of Arctic entomology happening around the world, and the Arctic is an area that is undergoing rapid environmental change.   It’s good that scientists are paying attention, and that entomologists are doing high quality research in the north.

Deciding on an “editor’s pick” for this issue was difficult as there were many excellent papers to choose from.  However, I ended up selecting Gergely Várkonyi and Tomas Roslin’s paper titled “Freezing cold yet diverse: dissecting a high-Arctic parasitoid community associated with Lepidoptera hosts”.   These authors, from Finland, have presented a very nice study about some food-web dynamics occurring in Zackenberg, Greenland  – a truly high Arctic field site, and one that has a remarkable history of long-term ecological monitoring.  Their work is focused on unraveling some of the amazing interactions between Lepidoptera and their parasitoids, and this paper provides a “systematic effort to characterise the high-Arctic Hymenoptera and Diptera parasitoid community associated with Lepidoptera hosts”.   This is a great paper, and hopefully continues to inspire continued efforts to study entomology at high latitudes.

Greenlandic field station

I asked the authors some questions about their work and they kindly provided in-depth answers:

Q1:  What inspired this work?

TOMAS: What got me interested in Arctic predator-prey dynamics was the work of my friend Olivier Gilg. His exploration of the predator-prey dynamics among collared lemmings and their few and selected enemies of Northeast Greenland made me realize that in a species-poor environment, the impact of individual species on each other will be oh-so-much easier to disentangle than among the zillions of interactions typical of tropical and even temperate communities. Here if anywhere you can actually work out both the structure and inner workings of full food webs – which is the very the idea that we have now realized in our study. (And well, from a less scientific point of view, after visiting Northeast Greenland I also realized that this is the most beautiful area of the globe, and that there is nowhere else that I would rather work.)

GERGELY: I have been interested in northern insects, especially hymenopteran parasitoids, since a very long time. I did my PhD in a subarctic environment in Finnish Lapland, with the main focus on host-parasitoid population dynamics between periodic moths and their enemies. I first encountered Greenlandic ichneumonids when my former teacher in ichneumonid taxonomy – and current friend – Reijo Jussila worked on the descriptions of some new species from the Scoresbysund area in Northeast Greenland. More than a decade later, Tomas asked me to identify some samples from Traill Island (NE Greenland), where he had initiated a pilot project on Lepidoptera-Hymenoptera food webs. The next step was when he invited me to join his project about to be launched at Zackenberg. The rest is history…

Q2:  What do you hope will be the lasting impact of this paper?

TOMAS: What I hope that we have achieved are three things: to expose the importance of versatile biotic interactions even in a harsh arctic environment, to reveal the massive effort needed to convincingly dissect even a simple food web, and to establish the baseline structure of a food web facing imminent climate change.

GERGELY: Could not say it any better. I can only add that I hope our thorough overview of the taxonomy and natural history of individual parasitoid species will contribute to getting a better understanding of who is who and what roles each species play in this arctic scene.

flowers in containers

Q3:  Where will your next line of research on this topic take you? 

TOMAS: While we have now figured out the structure of the Lepidoptera-parasitoid web, we should remember that this is but a small module of the overall food web of the region. Our current work aims at expanding/zooming out from this core web towards the full food web of the region, which should actually be more realistically doable here than anywhere else on the globe (see above). In this work, we try to make maximal use of modern molecular tools, offering new resolution to documenting trophic interactions.

GERGELY: Apart from the community ecology goals of this project, we will further continue to update what is known about the parasitic wasp fauna of Greenland. I am focusing on the Ichneumonidae, the single most species-rich family of Hymenoptera in both Greenland and the entire World. By combining morphology and molecular methods, I attempt to clarify species boundaries and detect potential cryptic species. The ultimate goal of this research is to compile a modern taxonomic overview of the Ichneumonidae of Greenland.

Q4: Any amusing anecdotes about this research?

TOMAS: Gergely used to wear a handy hiking suit of light coloration. One day he was almost shot as a polar bear after sneaking up on an unsuspecting colleague in the field.

GERGELY: Well, first of all I was not sneaking, just looking for adult wasps in a safe distance from this colleague of ours. She thought my net was a giant paw of a polar bear (!) and she was really scared for a short moment. But she was definitely not about to shoot me!

Mountain